The back-and-forth between the Republican nominee for president and the parents of a Muslim U.S. Army captain killed in the Iraq War continued Monday, after a weekend of verbal sparring that saw Khizr Khan, the father of Captain Humayun Khan, say Donald Trump has a “darkheart.”

Appearing on Morning Joe, Khizr Khan explained why he and his wife, Ghazala, decided to appear at the Democratic National Convention last week: “We felt compelled from within to [speak about Trump and how] voting for a divider, voting for an excluder will put such a burden on our souls for the remainder of our lives that we may not be able to bearit.”

Ghazala Khan also spoke, disproving Trump’s suggestion over the weekend that she didn’t speak at the DNC because she “wasn’t allowed to have anything to say.” Khan described the last time she spoke with her son, who told her of the great responsibility he felt for his fellow soldiers, but could hardly finish through hertears.

Meanwhile, Trump was on Twitter continuing to defend himself against the Khans, who received the support of 11 gold-star families over the weekend in an open letter that accused Trump of “cheapening the sacrifice made by those welost.”

Mr. Khan, who does not know me, viciously attacked me from the stage of the DNC and is now all over T.V. doing the same - Nice!

On CNN, Khizr Khan was asked to speak directly to Trump, who was clearly watching him make the rounds on TV. Khan said he wanted Trump to know that the billionaire has a serious problem with empathy. “Realizing, feeling the pains, the difficulties of the people you wish to lead and that is missing,” hesaid.

To Trump’s credit, at least he’s not smearing Khan. His former adviser and longtime friend Roger Stone did that over the weekend, though. On Twitter, Stone called Khan a “Muslim Brotherhood agent helping Hillary” and linked to a website that describes Khan as a “Muslim plant” working for Hillary Clinton on behalf of “Muslim oilcompanies.”

That probably isn’t sitting well with John McCain, who put out a statement this morning criticizing Trump for his remarks about the Khan family. It reads, in part, “I cannot emphasize enough how deeply I disagree with Mr. Trump’s statement. I hope Americans understand that the remarks do not represent the views of our Republican Party, its officers, orcandidates.”

That’s funny because Trump, as the party’s nominee for president, explicitly does represent the views of the GOP. While McCain, who describes profound respect for the Khans and their son, isn’t pulling his support for Trump, the statement does seem to contain a warning. “It is time for Donald Trump to set an example for our country and the future of the Republican Party. While our Party has bestowed upon him the nomination, it is not accompanied by unfettered license to defame those who are the best amongus.”

The implication: If Trump keeps it up, he may lose McCain’s support. The question is whether Trumpcares.